I think the best way to approach miracles in our time is to say that they are occurrences that defy the reasonable expectations of understood technologies and/or seem to demand the experience of a sense of wonder. Miracles change how we understand the world. That which was once a miracle may not be a miracle once the new understanding becomes common knowledge. Television was miracle, but is now not. This is an example of a transitory miracle.
There are other miracles, such as birth, joy, agreement, love and the like which are well within out technological capabilities, yet still demand the experience of wonder. These could be termed common miracles.
Another type of miracle would be the uncommon miracle. The re-growth of a human hand would be considered an uncommon miracle. These are the claims of many biblical miracles (i.e. raising from the dead, parting the sea, etc.). They are miracles in that certainly defy technological expectations. They are uncommon in that they appear to be impossible due to the fact that they are not generally repeatable even if they are claimed to have happened. Also, even if they seem impossible they would have to have a physical basis to have occurred and thus would simply become a transitory miracle once there was more understanding of the technology. In either case healthy skepticism should avoid taking actions that depend on an uncommon miracle for success. Our skepticism however should always allow for the transitory miracle to be discovered by available technologies.